There are a variety of xe2x80x9cmass storagexe2x80x9d or xe2x80x9ctape libraryxe2x80x9d systems, consisting generally of one or more recording/reproducing tape drives, a number of tape cartridges stored in bins, and a robotics assembly for transferring cartridges to and from the tape drives and the cartridge bins.
Most of the typical mass storage or library systems are not xe2x80x9cexpandablexe2x80x9d, in that additional cartridges beyond their local storage capacity of cartridge bins must be inserted and removed manually. Those systems which offer expandability with some form of xe2x80x9cpass-throughxe2x80x9d or conveyor system are generally slow, difficult to access for maintenance, or are suitable only for very large data-warehousing applications.
Accordingly, there has been a need for a simple self contained means of mechanically transferring cartridges between adjacent distinct library systems to increase overall mass storage system capacity, and one which can be easily installed and expanded in an installation at a customer""s site. The above referenced patent application fulfills the need for a simple self contained inter-cabinet transfer unit which is relatively simple and easily installed between two or more cabinets of respective tape handling library systems. The inter-cabinet transfer unit employs a movable tape cartridge bin assembly which is moved between the cabinets whereby the movable bin assembly and cartridge is presented to a typical cartridge handling robot of respective library systems as if it were part of the typical stationary bin array housed within the associated cabinet.
To this end, the inter-cabinet transfer unit of the above mentioned application is configured to work in conjunction with, for example, from two to four library systems generally contained in 24-inch rack cabinets, such as the DST-712 library system manufactured by Ampex Corporation, Redwood City, Calif., or with for example, one, two or more DST-712 library systems and a DST-812 library system also manufactured by Ampex Corporation.
More particularly, the inter-cabinet transfer unit includes a base channel as a support means which extends between adjacent library systems in a two library system configuration, or through a third or fourth library system in a three or four library system configuration. A movable bin assembly is translatably supported by the base channel, is horizontally movable rapidly between the library systems and is stopped accurately and repeatedly at preset xe2x80x9cdepotsxe2x80x9d, with one depot within each cabinet of the library systems for a respective transfer unit. A drive means, consisting of, for example, a motor driven cable drum and cable causes the rapid and accurate movement of the bin assembly between a depot in each respective library system. The depot locations (that is, the bin assembly) are addressed by each cartridge handling robot as if they were permanent addresses within the respective stationary bin arrays. Optical sensors associated with each depot verify the arrival of the respective bin assembly at each stop location. An optical sensor also determines whether a cartridge is present in the bin assembly at any of the depots. The inter-cabinet transfer unit provides for the retrieval and loading of a cartridge in a constant orientation relative to the movable bin assembly and the stationary bin array.
As may be seen from the disclosure in the above-mentioned application Ser. No. 09/293,007, the described inter-cabinet transfer unit is capable of transferring cartridges horizontally between adjacent cabinets. That is, it allows the expansion of for example the DST 712 and/or DST 812 library systems of previous mention into rows, utilizing the movable cartridge bin assembly which is horizontally translatable between stop locations (depots) in each library system.
The inter-cabinet transfer unit is preferred for relatively smaller mass storage systems, but is inadequate for larger mass storage systems formed of a larger number of tape library systems, since it requires all cabinets to be adjacent to each other in one straight line, that is, in side-by-side relation. This may not conform to the space limitations of the customer. Also, the inter-cabinet transfer unit must be xe2x80x9cskeweredxe2x80x9d through the sides of the cabinets during installation, which thus becomes more difficult if a larger number of cabinets are to be linked together.
Accordingly it would be highly advantageous to be able to expand the number of library systems in a mass storage system in other than a straight line, that is, other than in a continuous row. For example, a more convenient and footprint efficient multiple cabinet configuration would consist of a multiple row arrangement wherein cabinets are positioned in two or more rows, that is, in a front-to-back relation, to define a square or rectangular foot print.
The present invention overcomes the single row arrangement limitations of the prior inter-cabinet transfer unit by allowing multiple rows of library systems to be assembled in a more preferred compact configuration. To this end, the present invention, referred to herein as an xe2x80x9cinter-rowxe2x80x9d transfer unit, is designed to connect one of the DST 712 library systems, disclosed in the aforementioned application Ser. No. 09/293,007, to another DST 712 library system located directly behind it. Both cabinets are faced in the same direction with an access space (in this case, 3 feet) between them. A movable cartridge bin assembly, accessible to the cartridge handling robot of the first cabinet, is transported vertically up through the top of this cabinet, then horizontally until it is positioned over the second cabinet, and then vertically down until it is accessible by the cartridge handling robot of the second cabinet.
The advantage of this inter-row transfer unit is that it can link two parallel rows of DST 712 library systems, or DST 712 and DST 812 library systems. If a number of library systems are arranged in each row, then the cabinets within each row also are connected with the xe2x80x9cinter-cabinetxe2x80x9d transfer unit in the manner and configuration disclosed in the application Ser. No. 09/293,007. This combination of inter-row and inter-cabinet transfer units permits a xe2x80x9cgridxe2x80x9d or rectangular arrangement of the library system cabinets, which is more suitable for most installation spaces, and minimizes the distance a cartridge must travel between extreme bin locations.
The inter-row transfer unit of the present invention, and thus the movable bin assembly thereof, is situated immediately above the inter-cabinet transfer unit and thus does not interfere with its function. Therefore, the inter-row transfer unit of the present invention can be installed over any pair of DST 712""s in a front-to-back grid. Also, the respective ends of two of these inter-row transfer units can be installed in a respective DST 712 located in a middle row of library systems, with the respective end of one unit extending to a second row in front, and an end of another unit extending to a third row behind. Thus, a mass storage system arrangement of three or more rows of library systems is possible.
Having the inter-row transfer unit located above the cabinets yields several other advantages. For example, adequate headroom (6xe2x80x25xe2x80x3 or 1.96 m) is provided over the corridor between rows of cabinets, front and rear access to the cabinets is not compromised and installation of the inter-row transfer units is simplified.
Furthermore, since all cabinets are faced in the same direction, there is no necessity to turn or rotate the cartridge during the loading and retrieving processes, as is the case in most existing large library systems. The fact that the cartridge is handled with a constant orientation during loading and retrieving allows the use of a simpler and more reliable cartridge handling robot as well as bin assembly.
With regards to the mechanism of the inter-row transfer unit of the invention, the movable bin assembly is slidably supported on a shaft secured within a housing which extends between two front-to-back cabinets, generally of respective rows of cabinets of corresponding library systems. A cable drum/cable drive means mounted within the housing provide for the movement of the bin assembly, which is suspended from two bearing blocks by means of two pairs of support links. The combination bin assembly, support links and bearing blocks comprise a vertically/horizontally moveable xe2x80x9cbin assembly carriagexe2x80x9d which, in a preferred embodiment, is capable of being vertically as well as horizontally translated via a single drive means. Vertical translation of the bin assembly and cartridge is provided by opposing motion outward of the bearing blocks to raise the bin assembly, and opposing motion inward to lower the assembly, as is fully described below. The same cable drum/cable drive means provides the vertical movement of the bin assembly into and out of each library system as well as the horizontal translation between rows of library systems of the bin assembly carriage, formed of the bin assembly, supporting links and bearing blocks as a unit.
In a preferred embodiment of the invention, the drive means employ a single motor and cable drum, a single cable and a xe2x80x9ctrapdoorxe2x80x9d mechanism which enables the vertical motion, as well as the reversal of the horizontal translation of the bin assembly carriage, using the single cable and motor/cable drum drive means.
An alternative embodiment of the invention employs a pair of cables and respective pair of motors/cable drums as the drive means mounted within the housing, whereupon the xe2x80x9ctrapdoorxe2x80x9d mechanism is not required.
In another alternative embodiment, the pair of bearing blocks, the counter rotating links and the suspended bin assembly are replaced with a cartridge bin assembly carriage formed of a bin assembly affixed to a solid plate which in turn is slidably supported via a linear bearing block on a square or splined shaft mounted within the housing. The bin assembly and cartridge are lifted from, and lowered into, a cabinet by rotating the shaft 90 degrees with a second motor or the like. A cable drum/cable drive means provide for translation of the bin assembly between library systems.